Building for Esp32 appears this Warning:
.pio/libdeps/esp32dev/PubSubClient_imroy_/src/MQTT.cpp: In member function 'virtual MQTT::message_type MQTT::Publish::response_type() const':
.pio/libdeps/esp32dev/PubSubClient_imroy_/src/MQTT.cpp:602:3: warning: control reaches end of non-void function [-Wreturn-type]
}
^